Funding is requested for the purchase of an array processor to facilitate research on a wide range of structural studies being carried out by the six senior investigators of this proposal. Enhanced computing speeds are required for a number of refinement problems in X-ray crystallography, for theoretical studies of protein structure and function, and for analysis of NMR results on proteins and nucleic acids. The need for the system is based both on the total computing power required for these projects and on the importance, in a number of applications, for rapid turn-around in real time. The major projects for which the array processor will be used include: quantum mechanical calculations on the visual pigment chromophore and energy minimization studies of antibody combining sites; structural refinement on protein crystals and the development of new refinement and phasing techniques in protein crystallography; the adenovirus capsid; X-ray diffraction studies of filamentous bacteriophage and; the use of distance geometry and NMR data to determine nucleic acid structures.